The problem can be corrected by upgrading the affected package to version 4:4.3.8-3ubuntu7.8. After performing a standard system upgrade you need to reload the PHP module in the webserver by executing

sudo /etc/init.d/apache2 reload

to effect the necessary changes.

Details follow:

An integer overflow was discovered in the exif_process_IFD_TAG() function in PHP4's EXIF module. EXIF tags with a specially crafted "Image File Directory" (IFD) tag caused a buffer overflow which could have been exploited to execute arbitrary code with the privileges of the PHP4 server. (CAN-2005-1042)

The same module also contained a Denial of Service vulnerability. EXIF headers with a large IFD nesting level caused an unbound recursion which would eventually overflow the stack and cause the executed program to crash. (CAN-2005-1043)

In web applications that automatically process EXIF tags of uploaded images, both vulnerabilities could be exploited remotely.